A series of degradable block copolymers, poly(acrylonitrile)-b-poly(epsilon-caprolactone) (PAN-PCL), have been synthesized by sequential living polymerization in this study. Well-defined, microphase-separated PAN-PCL microdomains can be efficiently achieved in the bulk by using appropriate solvents. The microphase-separated lamellar samples were then used as templates to produce mesoporous carbons at which large amounts of porous texture in carbonized PAN matrix were formed after degradation of PCL due to randomly oriented lamellar texture (namely, interconnection of PCL microdomains). The thermal profiles for efficient stabilization were examined by differential scanning calorimetry and thermogravimetric analyses as well as Fourier transform infrared spectroscopy. Consequently, mesoporous carbon materials might be prepared as evidenced by transmission electron microscopy, field emission scanning electron microscopy, and small-angle X-ray scattering. The formation of carbonized materials was identified in accordance with the presence of carbon diffractions by wide-angle X-ray diffraction. In contrast to the thermal stability of the carbonization of PAN homopolymers, it is noted that the carbonization procedure can be achieved in the PAN-PCL system regardless of the stretching process (that is an essential process to improve the thermal stability of PAN carbonization). We speculate that this unique feature for the carbonization of PAN copolymers might be attributed to the stretched chains of PAN under nanoscale confined environment.